Light-sensitive strip material, e.g. photographic film or paper, a polyester printing plate, or another light-sensitive strip material, can be packaged light-tightly by winding it as a coil on a hollow supporting core, and by attaching a rigid, opaque flange to each end of the core, thus forming a light-tightly packaged roll. The diameter of the flanges is preferably larger than the diameter of the coiled material. A flexible circumferential cover may be secured to the coiled strip material and may cover the coiled strip material by a few complete coils. Preferably, the circumferential cover has a width in excess of the coiled strip material. The side ends of the circumferential cover may slope slightly upwards where they touch the flanges. In this way, a few coils of the circumferential cover shield the light-sensitive strip material from light. It is not required to secure the circumferential cover to the flanges: the package as described above is reliably light-tight. Such a package is used e.g. for recording film marketed by Agfa-Gevaert N.V.
As shown in FIG. 1, the flanges 20 in such a package have a slightly conical hub 23 having outside ribs 24 approximately parallel to the axis 26 of the flange 20. The flanges 20 are pressed into the hollow core 10 and remain attached to the core 10 because of a press fit, i.e. the outside diameter of the hub 23 including the ribs 24 is larger than the inside diameter of the core 10. The ribs 24 serve two purposes: keeping the flanges 20 attached to the core 10 on the one hand, and preventing the flanges 20 from rotating with respect to the core 10 on the other hand. The latter is required because the roll is driven via the flanges 20 in some cooperating apparatuses in which the roll is placed. Usually, these cooperating apparatuses dispense light-sensitive strip material from the roll.
The attachment of the flanges to the core described above, however, presents a problem of reliability. The attachment is not reliable because the dimensional tolerances of the flanges and the core are critical. A flange may become detached from the core due to shocks during shipping, or due to relaxation of the core (the core is usually made of cardboard) or by someone lifting the roll by one of its flanges, etc. If a flange becomes detached, the light-sensitive strip material is exposed, whereby the roll is wasted.
Patent FR-A-1 236 361 discloses a coupling part that supports a roll of strip material; the coupling part will be referred to as "flange" below. As shown in FIG. 2, the flange 20 has in the direction of its axis 26 a number of triangular protrusions 25 that are slightly inclined at the side of the centre of the roll and steeply inclined at the side of the end of the roll. In this way, the flange 20 can be inserted into the hollow, cardboard core 10 of the roll, and, once attached, cannot be removed from the core without damaging the core. Because of the protrusions 25, the core 10, and thus also the roll, cannot rotate with respect to the flange 20.
While this attachment may solve the problem concerning reliability, and while it may also allow the roll to be driven via the flanges, it still presents a problem. The flanges cannot easily be removed from the roll; removal damages the core.
Usually, such flanges are made of plastic, e.g. of polystyrene. Because of environmental considerations, it is highly desirable that the flanges can be removed easily from the roll, so that they can be re-used or recycled after the use of the roll.
In document DE-U-73 26 402, flanges are disclosed that are used during shipping of rolls of e.g. textile fabric or material for carpets. First, the fabric is wound onto a core, that is made of cardboard. Then, two identical flanges are inserted, one flange into each end of the core. Subsequently, the roll is shipped; when the roll is handled, e.g. by a forklift truck or another machine, it can now be handled by means of the flanges, so that damage to the roll is avoided; this is the purpose of the flanges. Subsequently, before the roll is put onto the equipment on which it is to be used, the flanges must be removed from the core, since the core is put directly onto the equipment.
FIGS. 3a and 3b show a flange 20 as disclosed in this document; FIG. 3a is a side view, partially showing a section, and FIG. 3b is a top view. The flange 20 has a disc portion 21 and a hub portion 23. The hub portion 23 contains screw thread 30 in the hub area near the disc portion 21; the screw thread has a steep slope (which corresponds to a small angle .lambda. in FIG. 4) so that a very large force is required to pull a flange out of the core in which it is inserted. The end 27 of the hub portion 23 that is away from the disc portion 21 has a sharp chamfer. The disc portion has either protruding elements 28 or holes 29.
A flange 20 is inserted into a core 10 (not shown in FIGS. 3a and 3b) as follows. First, the chamfered end 27 of the hub portion 23 of the flange is pressed into the core and then the rest of the hub portion 23, as far as the start of the screw thread 30. Then, the remaining portion of the hub portion 23, i.e. the portion containing the screw thread 30, is screwed into the core by means of a tool. The tool includes a lever, so that a high torque can be applied; the tool either has holes that fit into the protruding elements 28 of the disc portion 21 or has protruding elements that fit into the holes 29 of the disc portion 21. The core does not contain screw thread; when screwing the flange 20 into the core, a screw thread is cut or pressed into the core that corresponds to the screw thread 30 of the flange 20.
To remove the flange 20 from the core, the same tool is used to screw the flange out of the core.
This system presents the disadvantages that large forces have to be applied and that a special tool is required to insert a flange into the core and to remove it from the core.